Within hours of launching Chrome for iOS, the 'Safari-ized' browser took the top spot on the App Store's free download chart.

Google Chrome, released yesterday for the iPhone and iPad, has already snatched the top spot in Apple's App Store.

As of 11 a.m. ET Friday, Chrome held the No. 1 position on both the iPhone and iPad free app download lists.

Google launched Chrome for iOS on Thursday, first announcing the browser at its Google I/O developers conference early in the day, with the app showing up several hours later on Apple's App Store.

Reviews for Chrome have been overwhelmingly positive, with 80% of the more than 3,700 posted so far giving the browser a five-star rating, the highest possible. The average rating is four-and-a-half stars.

The numbers are impressive in light of the fact that Chrome on iOS is essentially Safari in disguise. Because of the rules Apple enforces, all Web-accessing apps, including browsers, must use Safari's rendering engine and iOS's stock JavaScript engine.

In effect, Chrome for iOS is a "skin" -- of Google's user interface (UI) and additional features -- covering Safari.

Benchmark tests run by numerous websites have confirmed that Chrome for iOS is dramatically slower than Safari in handling JavaScript due to the latter's use of a much-improved engine, dubbed "Nitro," that Chrome cannot access. Apple first used Nitro, which includes a "just-in-time," or JIT, compiler with the March 2011 release of iOS 4.3.

All desktop browsers now rely on a JIT compiler to significantly speed up JavaScript execution; many advanced websites and most Web apps depend heavily on JavaScript, so a JIT compiler will render those pages and run those apps much faster.

Google, however, was prevented by the App Store rules from using its own V8 JavaScript engine, which has a JIT compiler. Instead, it had to call the stock WebKit JavaScript renderer, which lacks a JIT compiler.

Some of the App Store reviewers noticed.

"Runs 3.5 times slower doing JavaScript than Safari thanks to the lack of Nitro," said a reviewer identified only as "Reviewergoy" yesterday. "Stick with Safari, folks. Google obviously half-assed another iOS app."

But browsers on other mobile platforms, notably Google's own Android, are also going sans Flash: Chrome for Android, which Google launched in beta in February and shifted into its "stable" channel earlier this week, also lacks Flash.